1. Technical Field
The present invention relates to growth-enhancing compositions and improved methods of use thereof for propagating grass plants, such as sterile grass plants, of the Class Monocotyledonae, including those of the family Poaceae.
2. Description of the Related Art
Certain monocot grass plants are useful as biomass crops, among other uses. One monocot, Arundo donax, or Giant Reed, of the Order Poales and the Family Poaceae (Gramineae), is one of the largest grasses in the world, and is an attractive, robust, perennial reed (Tucker, J. Arnold Arb., 71:145-177, 1990). The very strong, somewhat woody, clustering culms, which grow from horizontal knotty rootstocks, are known to grow to a height of 8-10 meters (see, e.g., Bailey, Manual of cultivated plants: Most commonly grown in the continental United States and Canada, Rev. Ed., MacMillan, New York, (1954); and Mabberley, The plant-book: a portable dictionary of the vascular plants, 2nd Rev., Cambridge Univ. Press, Oxford, 1997). Giant Reed is one of the largest of the herbaceous grasses and has fleshly, creeping rootstocks that form compact masses, from which arise tough fibrous roots that penetrate deeply into the soil. The culms commonly branch during the second year of growth and are hollow with walls of 2 to 7 mm thick.
The plant is known by a variety of common names, including carrizo, bamboo reed, Danubian reed, donax cane, Italian reed, Provence cane and Spanish reed. A. donax probably originated from the freshwaters of the warm regions of eastern Asia. It has been in cultivation in Asia, North Africa, and the Middle East for thousands of years and also in North and South America, Australia and South Africa, during the past century. Further information on the culture of A. donax can be found, for example, in U.S. Pat. Nos. 6,389,746; 7,303,916; Bell, Ecology and management of Arundo donax, and approaches to riparian habitat restoration in Southern California; in Plant Invasions: Studies From North America and Europe, Brock et al., Eds. pp. 103-113, Backhuys Publishers, Leiden (1997); Perdue, Econ. Bot. 12:368-404 (1958); Rossa et al., Bot. Acta, 111:216-221, 1998; Roys, Ethnobotany of the Maya: The Department of Middle American Research. M.A.R. Series Pub. 2, Tulane U., New Orleans (1931); Zahran et al., The vegetation of Egypt. Chapman & Hall, London (1992); and Zohary, Plant Life of Palestine. Ronald Press, New York (1962).
Plants from the Class Monocotyledonae, such as A. donax, are multipurpose plants. Giant reed, for example, has been used for over 5,000 years in making pipe instruments, and to this day remains a primary source of reeds for clarinets, organ pipes, and other woodwind instruments.
Giant reed is also used for erosion control and has great potential for use as an energy crop (see, e.g., Szabo et al., J. Anal. Appl. Pyrolysis. 36:179-190, 1996). The culms are also used for fishing rods, walking sticks, mats and lattices in the construction of adobe huts. Giant reed is also a source of industrial cellulose for paper and rayon making, and for the production of other polysaccharides (Neto et al., Ind. Crops & Prods. 6:51-58, 1997). It has also been considered as a source of pulp for the making of paper.
Giant reed grows very rapidly. When conditions are favorable, growth at a rate of 0.3 to 0.7 meter per week for several weeks is not unusual. Young culms typically grow to their full diameter within the initial growing season, but their walls increase in thickness thereafter.
Outside its native range and the Mediterranean, however, the plant is sterile; it flowers, but does not produce viable seed. Instead, it reproduces vegetatively from fragments of stems and rhizomes (see, e.g., Boose et al., Weed Res. 39:117-127, 1999). Hence, there have been considerable difficulties in reliably and efficiently propagating these plants.
Traditional horticultural propagation of giant reed is by division of rhizomes. However, the propagation of giant reed by either rhizome division, or by traditional seed culture, requires a significant amount of time and effort between the initiation of division, or planting, and the successful establishment of a growing plant. Moreover, conventional methods of propagation provide limited opportunity for genetic manipulation, and, in the case of seeds, do not permit genetic control of the resulting progeny. Such conventional techniques also require large areas for the production of a sufficient number of plants to be useful in programs for the production of fuel or biomass, or for use in bioremediation programs.
A number of particular propagation methods have been developed for grass plants such as sterile grass plants. Such methods include layering, stooling, root division, tissue culture, cuttage, root culture, and sectioned node culture. However, even though these methods have been widely-used over the last two decades, they are neither efficient nor cost-effective, in part because propagation cycles are too long, and only a limited number of propagules can be created in a given amount of time and a given amount of space. Also, certain of these methods lead to somalclonal variation, a serious disadvantage in operations that require clonal uniformity.
Giant reed is only one of the monocots that exhibit such multiple uses. Whether used as ornamentals, sources of energy, or as useful vehicles to carry out industrial processes, such grass-like plants are important. Accordingly, it would be useful to provide a method by which grass plants of the Class Monocotyledonae could be propagated even in areas in which plants of these genera are sterile and in a manner that would require shorter time, less effort and less area than conventional methods. The present invention provides these and other advantages.